# What is mFT FoV?

Started Jan 27, 2013 | Questions thread
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Re: practical measurement with 20mm

Detail Man wrote:

Anders W wrote:

Sure. But a I am already satisfied with 6.7% accuracy, and I would rather spend the time on figuring out the lighting for my next project, instead of figuring out how many inches I can fit in the frame to the first decimal.

Why did you do the exercise in the first place then? The error you made is sufficiently large to explain the entire discrepancy between the official specs and the value you found. And had the discrepancy been real, it would have been large enough to suggest that the official specs refer to the FoV before rather than after correction (which is not the case). So what was the point of your test as a response to gollywop?

In physical sciences a significant fraction of measurements and calculations is done approximately, rather than exactly. One continually weighs the expense of an accurate calculation vs. the practical advantage of the added accuracy. Gollywop said that the corrected image is significantly smaller than the uncorrected one. I got a quick, but approximate estimate of the AOV of the corrected image, and found it insignificant for my purposes (under 10%). At that point there was no reason for me to go on with a more accurate estimate.

The deviation is

(17.374582388429978-16.21875)/17.374582388429978*100 = 6.7%

If only you had used just ... a few ... more digits following the decimal-point in your calculations !

Now DM and Anders, you just quit playing around with a real scientist.  Why, back when I worked at the National Bureau of Standards, we used to be plenty happy when we got within 20% of the answer, particularly when we didn't know what the answer was that we were within 20% of.

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gollywop

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